Testing device



-May' 15, 19456 W. H. CUMMINGS TESTING DEVICE Filed Sept. 9, 1942 fiagllrg'lld T est Set INVENTOR WE Gun m2 BY Q i498 0 Q mun 0% I I m m awn's" l vW1 lliamllenry Gummings, SanAntcnio,'IZer., as.- I signer taAmeric-an Telephone. and Telegraph. Co nnany,,. a.ccrnoration oiNemYork.

l I Application September 9, 1942 Serial No. 457,720 I r I I frc'laimpwl.115-4183.)

- This ihvention to testing apparatus and more particularly to apparatus for detecting faulty 'insulatiom or leakage 'eo'nditiorrs; oncertain types of electrical conductors: r

..'I'he=.-arrangement's of the invention are particularly; adapted 'for testing electricak conductors at a. telephone switchboard, such: fonex'amble as a. private branch exchanger The typesof lines which may be tested for faulty insulation condi tionsratthe switchboard might be 'cords, trunks or station lines. One of the features of the test set of thi'sinvention consists in utilizing a power supply source at the switchboard to produce the I testing current. Another feature of the invention consists in providing a visual signal in the test set for indicating the presence of faulty insulation conditions ona line. v For example, a gasfilled discharge tube might provided which would following manner. .16

accompanying drawing in the figure of which is shown a circuit diagram illustrating a preferred form of the invention.

In the drawing there is shown enclosed in .not believed necessary to illustrate other apparatus at the switchboard in explaining the arrangements of the invention. At the right of the drawing there is shown enclosed in dotted lines the'test set of this invention. It comprises a jack J3 which may be. connected by the patch cord I to jack J1. The jack J3 is connected to the vacuum tube rectifier 4. Connected to the rectifier is a gas-filled discharge tube 5. The a1- ternating current from source 3 is rectified by tube 4 and applied to the gas-filled tube '5. Its operation is controlled by the condenser I and the presence or absence on the line being tested of 'a faulty insulatiorr' condition=- as hereinafter pointed out. GOnderiser 1 might; for purposes of illustration have avalue-of twomicrofarad's. A resistance '8 is provided to prevent the connec tion-jofthetest'set to a line from causing any interference with apparatus; suohasya bell; at a station connected to the line. A jack J4 is pro vided which may :be connected by patch-cord 2 toe thejack: Ja of a line tobe tested'i Theplug Bit might be connected to jack; J 4L if: the: operators cord oiroui-tgwas. to be tested. A\ switch 9 is pro vided for reasons to be pointed out hereinafter.

The test set of the invention operates in the In order to obtain test current the patch cord l is inserted in jacks J1 and J3. This will connect the generator 3 to the tip and ring conductors of jack J3. This current will be rectified by the tube 4 and applied to the electrodes of the gas-filled tube 5. The voltage of this rectified current will be sufficient to break down the gas-filled tube and it will glow. Condenser 1 is in the path of current flowing through the gas-filled tube 5 and it will commence to charge up. When the condenser becomes charged the potential on the plate of the condenser connected to one of the electrodes of tube 5 will be equal and opposite to the potential applied to the other electrodeof the tube 5 and it will be extinguished. The patch cord 2 will now be inserted in jack J4 and jack J2 if the line connected to jack J2 is to be tested. 'If the operators cord circuit is to be tested instead of a line the plug P1 would be directly inserted into jack J4.

After the jack J2 is connected to the jack J4 the test man will operate the key 9 to either one of its two positions. If the key 9' is thrown in the upward position, as shown, a test may be made to determine whether there is any leakage to ground from the tip and ring conductors. With the key 9 in the upward position the tip and ring conductors are connected together to line 20 and thence to the right hand side of charged condenser 1. Ground at generator 3 is connected to the other side of condenser I over conductor 2!. Accordingly if there is a leakage to ground from either the tip or ring conductor under test a circuit will be completed thereover to discharge the condenser 1. If this leakage is large the condenser discharges immediately and will not accumulate a new charge from tube 5 and tube 5 will be operated and glow steadily. If this leakage is comparatively small the condenser will discharge more slowly and eventually the charge thereon'will become small enough so that the tube 5 will be unblocked and flash. This operation of the tube will again start to build up a charge on the condenser until it is large enough to again block the tube 5 to cause it to go out. Hence if the leakage is comparatively small the tube will flashintermittently. Obviously if the insulation is perfect and no leakage to ground exists the charge will remain on condenser 1 and the tube 5 will remain dark.

If the key 9 is thrown to its downward position a test may be made to determine whether any leakage exists between the tip and ring conductors. If any leakage exists between the tip and ring conductors a circuit for discharging the condenser I will be established as follows: from the right hand side of condenser 1, conductor 20, ring conductor, leakage path between ring and tip conductors, tip conductor, lower contact of switch 9, sleeve conductor and over conductor 2| to the left hand side of condenser I. ously if this leakage is large, such as a short circuit, the condenser will discharge at Once and will not accumulate a new charge and the tube 5 will glow steadily. On the other hand if the leakage is small, the tube 5 will flash intermittently. Obviously if there were perfect insulation be-' tween the tip and ring conductors the tube 5 would remain out.

Thus with the test set of the invention tests for various types of insulation or leakage trouble may be readily made. While the invention has Obvibeen disclosed as embodied in certain specific forms which are deemed advisable, it is understood that it is capable of embodiment in many other and widely varied forms without departing from the spirit of the invention as defined by the appended claim.

What is claimed is:

Arrangements for testing faulty insulation conditions in a, line including a source of alternating current, a circuit having conductors connected to the terminals of said source, a ground connected to one of the terminals of said source, a rectifier and a gas filled discharge tube and a condenser connected in series with each other in said circuit, and switching means for so connecting one side of said condenser to the tip and ring side of the line to be tested that if a ground exists on either said tip or ring a circuit for discharging said condenser will exist between said last mentioned ground and said first mentioned ground and the operating condition of said gas filled discharge tube will be changed and for alternatively so connecting said condenser across the tip and ring of the line to be tested that if a leakage path exists between said tip and ring a circuit will be completed for discharging said condenser across said leakage path and the operating condition of said gas filled discharge tube will be changed.

WILLIAM HENRY CUMMINGS. 

